I am not sure of the setup you are using but I will offer you a used 4.5 inch drum - inside width is 4 inch wide and about 2.75 inch high from the inside diameter. It doesn't have a built in brake groove but I can give you a flywheel that will work with a brake belt that can be mounted on the shaft either side of the drum. If you are using a ford long shaft starter motor with a 6.25 inch long shaft this will work just fine. I used this setup on one of my winches and then decided I wanted a bigger drum that would hold more line for those really big flying fields.

I will give you the drum and fly wheel for free - all you have to do is pay for the shipping cost. If you do not find what you are looking for and decide you want to take me up on this offer, PM me your address and I will ship it to you. If you need a couple pictures let me know.